[sudoku] Fix validation not ending the game
[sudoku] Fix validation not ending the game

If something is failing silently, then you probably missed an await
somewhere. To help catch these errors, you can enable asyncio's debug
mode by setting the env variable PYTHONASYNCIODEBUG to 1, or by calling
client.loop.set_debug(True).

Ikusaba-san/Chiaki-Nanami